Heretofore, an analyzing laboratory or an in-line analyzer using typical metal particle detecting technology has employed one or more of the spectrophotometric, irradiation light attenuating, electrical resistance, and magnetic resistance types of metal particle detection technology. However, with this technology, the following problems have occurred:
(1) The spectrometric type technology can detect substantially all kinds of particles so as to obtain the quantity of particles in each of the kinds. However, a large scale detecting apparatus has to be used, and accordingly, it is not appropriate for use in in-line analysis. Furthermore, with this technology, it is impossible to estimate or detect the number of particles per particle size; PA1 (2) The irradiation light attenuating type technology can detect substantially all kinds of particles so as to obtain the quantity of particles in each of the kinds, and it is suitable for use in in-line analysis. However, it is impossible to estimate or detect the number of particles per particle size. PA1 (3) The electrical resistance type technology is suitable for use in in-line analysis, but its detection errors are large. Further, it is impossible to estimate or detect the number of particles per particle size. PA1 (4) The magnetic resistance type technology is suitable for use in in-line analysis. However, it cannot detect particles other than ferromagnetic material particles such as Fe or Ni. Furthermore, it is impossible to estimate or detect the number of particles per particle size.
Further, in Japanese Patent Application No. 2-83150, the inventors have proposed a metal particle detecting sensor with a simple structure using electric discharge. However, since a pair of comb electrodes used in this metal particle detecting sensor are composed of a pair of platinum thin film electrodes formed on an insulator by a vapor deposition process or the like, being slightly spaced from each other, it cannot estimate or detect the number of metal particles, in fluid, per particle size.